







Prove the earth is round 
20160130 

From Kevin: Working on a project for a science fair.
To prove the earth is round without the ability to get way above the surface.
How could we set up and experiment to see the curve.
My thought is using a telescope at the beach?
Form what we see so far the curve is 8 inches per mile?
So thought is set up a telescope and a target 1 mile away? Answered by Robert Dawson and Chris Fisher. 





Prove that you cannot factor x squared + 5 
20150528 

From lily: the question is: prove that you cannot factor x squared + 5 Answered by Robert Dawson. 





Percentage improvement 
20100826 

From shahrukh: Hi...
We had a web page that was taking 12 secs to load. Now it loads in 3 secs.
What is the percentage of improvement or how much faster is it working now.
TO me it looks like it is working 3 times faster or there is a 300% improvement in the loading time.
However my client says its ((123)/12*)100 = 75% improved. Which seems illogical on the face of it.
Thanks for your help
Shahrukh Answered by Robert Dawson and Chris Fisher. 





Prove A intersect B =X iff A = X and B = X 
20100306 

From Gloria: how would you prove A intersect B =X iff A = X and B = X Answered by Tyler Wood. 





Prove that the set of all positive odd integers is an infinite set 
20090620 

From Nazrul: How can I prove that the set of all positive odd integers is an infinite set.
Thank you in advance. Answered by Victoria West. 





Percent improvement 
20080612 

From JOHN: IF YOU HAD A RATE OF 678/HOUR AND YOUR NEW RATE/HOUR
IS NOW 1961 WHAT IS PERCENT OF IMPROVEMENT Answered by Penny Nom. 





The square root of 3 
20000404 

From Mr. William: Prove that root 3 is irrational Answered by Harley Weston. 





Percent of improvement 
20000130 

From Steve Quigg:
In a 1998 survey, 21% polled responded favorably to a question. In 1999, 31% responded favorably. What is the percent of improvement? Answered by Harley Weston. 





Two algebra problems 
19991217 

From Michael Standfest: If x+4 is a factor of 2x^{4}+kx^{3}3kx^{2}+6x40, find k and Prove that n^{2}n is even for all n, using the proof of contradiction Answered by Penny Nom. 

